package com.hmdp.service.impl;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONUtil;
import com.hmdp.dto.Result;
import com.hmdp.entity.Shop;
import com.hmdp.mapper.ShopMapper;
import com.hmdp.service.IShopService;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.hmdp.utils.CacheClient;
import io.netty.util.internal.StringUtil;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;
import org.springframework.util.StringUtils;

import javax.annotation.Resource;

import java.util.concurrent.TimeUnit;

import static com.hmdp.utils.RedisConstants.*;

/**
 * <p>
 *  服务实现类
 * </p>
 *
 * @author 虎哥
 * @since 2021-12-22
 */
@Service
public class ShopServiceImpl extends ServiceImpl<ShopMapper, Shop> implements IShopService {
    
    @Resource
    private StringRedisTemplate stringRedisTemplate;
    
    @Resource
    private CacheClient cacheClient;
    
    @Override
    public Result queryById(Long id) {
        ////缓存穿透解决方案
        //Shop shop = cacheClient.queryWithPassThrough(CACHE_SHOP_KEY, id, Shop.class, this::getById, CACHE_SHOP_TTL, TimeUnit.MINUTES);
        
        //互斥锁缓存击穿解决方案
        Shop shop = queryWithMutex(id);
        
        ////逻辑过期解决缓存击穿
        //Shop shop = cacheClient.queryWithLogicalExpire(CACHE_SHOP_KEY, id, Shop.class, this::getById, CACHE_SHOP_TTL, TimeUnit.MINUTES);
        
        if (shop == null) {
            return Result.fail("店铺不存在");
        }
        //返回
        return Result.ok(shop);
    }
    
    /**
     * queryById -- 缓存击穿解决方案（互斥锁）
     * @param id
     * @return
     */
    public Shop queryWithMutex(Long id) {
        String shopKey = CACHE_SHOP_KEY + id;
        //1.从redis查询商铺缓存
        String shopJSON = stringRedisTemplate.opsForValue().get(shopKey);
        //2.判断redis中是否存在
        if (StrUtil.isNotBlank(shopJSON)) {
            //3.redis中存在，直接返回
            return JSONUtil.toBean(shopJSON, Shop.class);
        }
        //判断命中的是否是空值null
        if (shopJSON != null) {
            //返回错误信息
            return null;
        }
        //4.实现缓存重建
        //4.1获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        Shop shop = null;
        try {
            boolean isLocak = tryLock(lockKey);
            //4.2判断是否获取成功
            if (!isLocak) {
                //4.3失败,休眠并重试
                Thread.sleep(50);
                return queryWithMutex(id);
            }
            //DoubleCheck
            //从redis查询商铺缓存
            shopJSON = stringRedisTemplate.opsForValue().get(shopKey);
            //判断redis中是否存在
            if (StrUtil.isNotBlank(shopJSON)) {
                //3.redis中存在，直接返回
                return JSONUtil.toBean(shopJSON, Shop.class);
            }
            //判断命中的是否是空值null
            if (shopJSON != null) {
                //返回错误信息
                return null;
            }
            //4.redis中不存在，根据id查询数据库
            shop = getById(id);
            //5.数据库中不存在，返回错误
            if (shop == null) {
                //将空值写入redis
                stringRedisTemplate.opsForValue().set(shopKey, "", CACHE_NULL_TTL, TimeUnit.MINUTES);
                //返回错误信息
                return null;
            }
            //6.数据库中存在，写如redis
            stringRedisTemplate.opsForValue().set(shopKey,JSONUtil.toJsonStr(shop), CACHE_SHOP_TTL, TimeUnit.MINUTES);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        } finally {
            //7.释放互斥锁
            unlock(lockKey);
        }
        //8.返回
        return shop;
    }
    
//    /**
//     * queryById -- 缓存穿透解决方案
//     * @param id
//     * @return
//     */
//    public Shop queryWithPassThrough(Long id) {
//        String shopKey = CACHE_SHOP_KEY + id;
//        //1.从redis查询商铺缓存
//        String shopJSON = stringRedisTemplate.opsForValue().get(shopKey);
//        //2.判断redis中是否存在
//        if (StrUtil.isNotBlank(shopJSON)) {
//            //3.redis中存在，直接返回
//            return JSONUtil.toBean(shopJSON, Shop.class);
//        }
//        //判断命中的是否是空值null
//        if (shopJSON != null) {
//            //返回错误信息
//            return null;
//        }
//        //4.redis中不存在，根据id查询数据库
//        Shop shop = getById(id);
//        //5.数据库中不存在，返回错误
//        if (shop == null) {
//            //将空值写入redis
//            stringRedisTemplate.opsForValue().set(shopKey, "", CACHE_NULL_TTL, TimeUnit.MINUTES);
//            //返回错误信息
//            return null;
//        }
//        //6.数据库中存在，写如redis
//        stringRedisTemplate.opsForValue().set(shopKey,JSONUtil.toJsonStr(shop), CACHE_SHOP_TTL, TimeUnit.MINUTES);
//        //7.返回
//        return shop;
//    }
    
    /**
     * 获取锁
     * @param key
     * @return
     */
    private boolean tryLock(String key) {
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }
    
    /**
     * 释放锁
     * @param key
     */
    private void unlock(String key) {
        stringRedisTemplate.delete(key);
    }
    
    @Override
    @Transactional
    public Result update(Shop shop) {
        Long id = shop.getId();
        if (id == null) {
            return Result.fail("店铺id不能为空");
        }
        //1.跟新数据库
        updateById(shop);
        //2.删除缓存
        stringRedisTemplate.delete(CACHE_SHOP_KEY + id);
        return Result.ok();
    }
}
